This invention relates to petroleum (oil and/or gas) pipelines and especially to equipment to insert and remove static monitoring devices in pipelines under pressure using wireline tools.
Wireline tools are commercially available and have been used to insert and withdraw various devices in conjunction with oil wells for many years. Wireline device uses include the insertion of instruments for measuring downhole pressure or temperature. Other uses also include the downhole mounting of pressure and flow control devices such as chokes and check valves.
In mounting a choke in a well, for example, the choke can be attached to a locking device and both attached to a running tool in the wireline lubricator. The lubricator is then mounted on top of a valve on the wellhead. The valve is opened and the locking device and choke are lowered into position and locked in place, typically in a seating (or landing) nipple which had previously been placed in an appropriate position. As the locking device and choke are locked in place, they are disengaged from the running tool (typically by a strong pull on the wireline after the locking device has been locked in the seating nipple). The running tool is then pulled up into the lubricator and the valve closed. The pressure can then be bled down and the lubricator disconnected from the wellhead.
If the choke is to be removed at some later time, the lubricator is remounted on top of the valve on the wellhead with a pulling tool (often a different tool than the running tool) inside of the lubricator. The valve is then opened and the tool lowered to engage the locking device and choke. The pulling tool unlocks the locking device from the nipple and the wireline is then used to pull the locking device back up into the lubricator. The valve is then closed and the lubricator pressure bled down. The lubricator with the retrieved locking device and choke may then be removed from the wellhead.
Lubricators, locking devices, running tools, landing nipples, and pulling tools are shown, for example, in the following U.S. Pat. No. 2,677,427, issued to McKinney et al., on May 4, 1954; U.S. Pat. No. 3,207,222, issued to Tamplen on Sept. 21, 1965; U.S. Pat. No. 2,887,163, issued to McGowen et al., on May 19, 1959; U.S. Pat. No. 2,920,704, issued to Fredd on Jan. 12, 1960; U.S. Pat. No. 3,294,173 issued to Hodges on Dec. 27, 1966.
Corrosion coupons have been inserted into pipelines, both with the line depressurized and under pressure. The depressurization of the pipeline at any time which coupons are to be inserted or retrieved is, of course, inconvenient and expensive.
One method of inserting coupon assemblies into a pipeline under pressure is by use of a hydraulic insertion mechanism such as shown in U.S. Pat. No. 3,718,034, issued to Swearingen on Feb. 27, 1973. Such a mechanism must remain mounted on the pipeline during the entire time the coupon assembly is inserted and thus each coupon assembly requires one complete mechanism. In addition, the mechanism is relatively thin and fairly tall (typically sticking up about 4 feet or more above the pipeline) and is very susceptible to damage, especially when left in an isolated location.
As an alternative to a hydraulic force for insertion, mechanisms such as a lead screw and crank can be used to supply the required force. Such mechanisms also remain mounted throughout the test and are generally even taller and thus more susceptible to damage.